Radio receiving system



Dec. 1I 1925.

J. B. BRADY RADIO RECEIVING SYSTEM Original Filed Dec. 28, 1921 n. lugo mman.:

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UNITED STATES 1,563,958 `PATENT oFFlcE.

JOHNVB. BRADY, OF SOMERSET, MARYLAND, ASSIGNOR TO MORKBUM COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF MAINE.

RADIO RECEIVING SYSTEM.

Original applicationled December 2.8, 1921, Serial No. 525,298. Patent N'o. 1,465,212, dated February 26, 1924. Divided and this application filed August 11, 1923. Serial No. 656,956.

To aU Iccf/0m it may concern: l

Be it known that I, JOHN B. BRADY, a citizen of the United States, residinof at Somerset, county of Montgomery, and btate of Maryland, have invented a certain new and useful Improvement in a Radio Receiving System, of which the following 1s a specification.

My invention relates broadly to the automatic transmission and reception of radio telegraph signals, and more particularly to a system for receiving radio telegraphlc signals directly in printed form.

This application is a division of my application berial Number 525,298 filed De cember 28, 1921, now Patent Number 1,185,212, dated Feb. 26, 1924.

The object of my invention is to provide a system of electron tube circuits and a mechanical arrangement of parts at a radio receiver for setting down received signals in type.

A further object of myinvention is to provide an impulse system of radio transmission and reception as distinguished from the present dot and dash code systems whereby to render substantially secret the messages transmitted.

A further object of the invention isr to provide a radio telegraph receiving system employing a printer receiver which may be operated by one without knowledge of codes as at present required to receive signals transmitted from a distant radio station.

A further object of the invention is to provide means whereby code combinations may be readily changed from time to time whereby to render the system substantially secret and thc code practically unbreakable.

Another object of the invention is to provide an arrangement of electron tubes at a radio receiver responsive to characteristic successions or groups of impulses with a set of power tubes arranged to deliver the received impulses to a circuit that controls a mechanical arrangement of parts for selecting characters represented by the particular groups of im ulses actuating the tube circuits and for efljeeting the prlnting of such characters.

The transmission system is adaptable for shore or ship station control and in modi.-Y

lied form for the control of aircraft radio transmitters from which an observer, can communicate to ashore or ship station by operating thelettered keys of a keyboard while the message appears simultaneously in printed type at the receiver.

The invention will be more clearly understood by reference to the accompanying drlawilngs and the following specification in wnc Figure 1 is a wiring diagram of the re' ceiving apparatus employed in this system; Figs. 2 and 3 are fragmentary views showing the mechanical arrangement of parts actuated by the electron tube circuits; and Fig. 4 is a diagrammatic representation of the character of impulse code employed in this system. The invention as set forth in the particular embodiment Shown in the ldrawings has been operated with considerable success, the transmitter being controlled bya keyboard and the characters being printed at the receiver at ratesof speed beyond that practicable by manual reception and translation. The system comprises broadly a transmitting unit having a source of continuous oscillations which may be an alternator, an arc, or an electron tube generator. The oscillations are modulated and controlled by a system of impulse transmission involving the starting and stopping of oscillations in an antenna system, or modulation thereof, in combinations of impulses in accordance With an impulse code. This impulse control is preferably secured by manual operation of a lettered keyboard, the keys of which are arranged to control the operation of a set of contacts so that the latter are either closed or opened through each of a definite number of successive time intervals for each character to be transmitted. The system` may utilize continuous waves, interrupted continuous waves or damped oscillations may be employed. The transmitter control is arranged. for approximately 31 combinationsv of impulses comprising the characters to be transmitted. The lenergy radiatedfrom the antenna s stem is practically irrecognzable on suc reception by ear as there 1s no order of dots and dashes as at present employed in radio tele raphy, the radiations being modiiedby t e controlling e011s or regenerative action is employed accord- -in to the nature of the waves being received. The energy is red-uced to a relatively low frequency and amplified through a plurality of stages of electron tube am 1- ication. At the final stage of am li cation, a power relay is inter-connecte comrislng a set of parallel connected 'tubes having a selectively tuned input c ircult and a mechanical relay actuated by the impulses of energy delivered by said power tubes. The relay is arranged to open and close a circuit containing a source of energy connected in series with the armature coils of an automatic Teletype printer receiver or other printer receiver utilizing impulse reception.

The Teletype equipment illustrated in connection with this system is the invention of Charles L. Krum and Howard L. Krum of Chicago, Illinois. This Teletype apparatus is described in an application filed in the U. S. Patent Oilice by these inventors December 23, 1918, Serial No. 346,948 and in other pendin applications, and some features of the te egraph system employed in connection with suchl apparatus are described in H. L. Krum Patents No. 1,286,351 dated December 3, 1918 and No. 1,434,290, dated Octobel 31, 1922. Reference is made to these patents andto the pending applications for the details of this equipment.

However, a general description is given herein.

At the distant transmitter a keyboard resembling the keyboard of a ty ewriter may be provided. The individual eys of this keyboard are formed in key bars pivoted at f the rear of the machine casing and arranged to be depressed by linger control. Beneath the key levers is arranged a set of five selecting bars arranged to be operated or set by the keys in different combinations. A sixth bar o erated by each key controls a clutch by w -ch a contact operating cam shaft is connected to a motor and so rotated through one revolution for each key depressed. The cam shaft is provided with a set of successively operatin cams which effect and time the operation o a set of contacts, such operation being so controlled by a set of selecting fingers operated by the selector bars, that the circuit controlled lby* the contacts is either opened or closed through a definite number, preferably live, successive time intervals for each character transmitted, and each character signal being preceded by a starting interval or impulse. That is to say, the contacts are uniformly operated at the beginning of each signal to form a starting impulse and through'the remaining tive intervals or units of each signal are either Lacasse opened or closed to form combinations of impulses representing characters to be transmitted. f In the case of an electron tube radio transmitter the grid circuit -may be opened andclosed in accordance with the` operation of the set of contacts. In the case an arc transmitter a uniwave signalling ke system may control the radiating impu ses, effecting or suppressing radiation of energy durin the successive time intervals of each si na In the case of an alternator 'amagnetlc amplifier may be controlled to start and-suppress the radiated impulses. This operation causes the radiation of impulses of high frequency energy from an antenna system. j

At the receiver an arrangement of electron tube circuits is provided whereby these impulses are reduced to a relatively low frequency, amplified and then caused to actuate a power relay from which they are delivered to the armature magnets of a Teletype printer.

The printer is controlled by a magnet having two coils which o erates an armature moved in one direction 'y the magnet and in the opposite direction by an adjustable spring. The printer mechanism is carried by a suitable frame, the moving parts of which are operated from a motor through the 'medium of a start and stop clutch which is initiated in o eration by the starting impulse or interval o? each signal. -A rotatlng selector actuator driven by the motor and thrown into operation by the clutch is adapted to osition a set of selectors in different com-` inations in accordance with the movement of. the armature of the controlling magnet, and which in turn is controlled by the combinations of impulses striking the receiving antenna system. The shaft carrying the selector actuator is also provided with a. transfer cam which at each rotation transfers `the setting of the selectors to a second set of selectors or seekers and restores the first set for the next o eration.

The main shaft which carries the selector actuator also carries a combiner wheel, a notched ratchet wheel and a type wheel. The seekers cooperate with the combiner wheel to control ajtrip lever which in turn effects the engagement of a printing dog 01' arm with the notches of the ratchet wheel and the latter forces a print roller carrying a paper strip against the letter of the type wheel corresponding to the setting of the seekers, the latter and' the print dog or arm being re-set or restored to normal at the end of each revolution of the main shaft by suitable cams mounted thereon. The combination of impulses striking the antenna system at the receiver thus control the operation of the printer mechanism to secure the impression of the characters represented by the lsignals upon a paper strip,

Referring more particularly to the drawings the ra 1o receiver comprises an antenna system 31, a primary receivmg inductance 132, series condenser 33 and ground 34. In-

ductively associated with the primary winding 32 is secondary winding 35 tuned by yvariable condenser 36. This its secondary Winding 52 connected to the input circuit of electron tube amplifier 48. The amplifier comprises electron tube 48 having filament 49, grid 50 and plate 51 and output circuit 53 and 56. The filament 49 is heated by battery 57. The winding 53 forms the primary for transformer 54, the secondary winding 55 of which is connected to the input circuit ofl electrontube amplifier 58. The electron tube amplifier 58 includes an electron tube having the filament 59 energized by battery 67, grid 60, and platc 61. The output circuit-includes pri lnary winding of transforn'ier 64 and high otential battery 66. The secondary winding 7 0 of transformer G4 connects to the input circuit of a power amplifier.

The power amplifier herein described by way of example in this system is the invention of F. W. Dunmore of Washington, D. C. The power relay comprises electron tubes 78 and 7 9 having their grid elements 80 and 81 parallel connected and their plate elements 82 and 83 parallel connected. The filaments 84 and 85 are energized from battery 87. A variable negative bias is placed upon the grids 80A and 81 by adjustable battery 72. The input circuit across the tubes is selectively tuned by condenser 71. The output circuit of the power relay includes armature' windings 9() of a mechanical relay, and high potential battery 86 the relay windings being shunted with by pass circuit 92. j The relay circuit is adjusted to respond sharply to the characteristically timed succession of impulses for each character signal. lThe mechanical relay 90 has an armature 93 and cooperating Contact 94 connected in circuit with battery 95 and to terminals BC upon the Teletype apparatus 22. The terminals BC beneath the base of the Teletype are connected through conductors 96 to the Teletype armature coils 99, each coil having terminals 97 and 98 with windings series connected. These armature coils as represented in Figs. 3 and 4 are mounted below a. pivoted armature 117 which in operation sets in motion the printer l mechanism to producey as a final result a printed character corresponding to the sequence of received impulses.

The Teletype printer comprises generically' a pair of armature magnets 99 which operate the magnet armature 117 mounted to move vertically'under the tension of an adjustable spring. The printer mechanism is carried by a frame supporting the moving partsand enclosing a clutch and brake mechanism to control the staiting and stopping of the mechanism on control of the received impulses. central driven shaft 118 carrying mechanism under control of the magnet armature for selecting and printing the particular character represented by the characteristically timed succession of received impulses. l

This is accomplished by a ring member 119 mounted on the central shaftto rotate there with but shiftable longitudinnally thereon under` tension of spring 120. The ring cooperates with an extension 121 upon the magnet armature, whereby the longitudinal position of the ring (forward or backward) is controlled in accordance with the movement of the armature, which in turn is controllcd by the impulsesstriking the receiving antenna system. Integral with this ring member is an arm 122 which carries at its outer extremity a shuttle'roller 123. The arm in its rotation about the central shaft moves the shuttle roller over a fixed cam ring 124 having a series of five indented portions around the surface thereof.

The speed of shaft 118 is Such that the shuttle roller 123 passes over the indentations of the cam ring 124 during the five selecting intervals of each signal. and either moves longitudinally into each indentation or is prevented from doing so in accordance with' the position of the armature 117, which is operated by the magnet 99 in response to the groups of impulses striking the antenna system.

Within the indents are mounted plunger-s 125 which are pushed forward when the shuttle roller moves into the corresponding recesses but remain in normal position when the shuttle roller is prevented from doing so b 1 the armature of the control magnet 99.

Mbunted upon the frame is a set of levers 126 which cooperate with selector pins 127 to cause longitudinal movement thereof when the plungers push forward under ac tion of the shuttle roller4 against one end of the toggle levers. The setting of the selectors is transferred by a cam on the central shaft to a set of five seekers having depending tongues which cooperate with a combiner wheel. The combiner wheel is mounted upon the central shaft which also carries a notched ratchet wheel and a type The printer includes a wheel. The combiner wheel and ratchet wheel are notched upon the periphery thereof in a manner corres onding to the impulse characterswhich ma e up the signals actuating the electron tube circuits. When the seekers have been set in position, atrip lever is operated causing a prlnt dog to mesh with the notches of the ratchet wheel and guide the print roller carrying a paper str1 a ainst the proper letter of the type whee roups of impulses striking the kantenna system at the receiver thus controls the printer mechanism to secure the slmultaneous selection of the corresponding character and the printing of the character upon a pager strip.

igure 4 lllustrates the character of the code employed in the present system. The characters are made up of live intervals or units of current or no current secured by the opening and closing of the transmitter circuit. The character A for example comprises two contact closures and three spaces or non-contact closures, making u the impulses 2, 3, 4, 5, and 6 upon operat1on of the transmitter contacts at the distant radio transmitting station. Correspondingly the characters B and C may be formed by a different order of sequence of the impulses illustrated in Figure 4. The transmitter keyboard at the distant station is provided with a shift key whereby characters may be transmitted on the upper case or the lower case, the type wheel at the recelver being controlled accordingly.

The generic arrangement of the control keyboard at the distant transmitter is shown in the drawings where the radio transmitter control circuit is designated 28 leading to the transmitter contact 29 and 30. These contacts comprise a set of six circuit closing contacts 1n parallel which are closed in a particular sequenceto secure the starting and stopping of radiation from the antenna system in accordance with the characteristically timed succession of impulses for the particular character to be transmitted. It will be suicient to state that the relation of the keyboard control with the operation of these contacts is that contact 1 formsv the starting impulse for the character'to be transmitted while contacts 2, 3, 4, 5, and 6 are closed in ropcr sequence through the cam-shaft nieclianism driven. by motor 100. '1`he motor 100 is maintained at approximately the same speed as the corresponding motor at the distant radio receiving station. The motor 100 has its speed governed by suitable means such as make and break contact 101 which breaks the motor circuit across a 1000 ohm shunt 102. The excessive sparking at the governor contacts is absorbed by condenser 103. The power supply for the motor is secured through circuit 104. This same motor drives the receiver ,chanical printing arrangement.

mechanical printer arrangement in approximate synchronism with the motor at the distant transmitting station.

The operation of the system has probably been made clear by the specification above but may be repeated here briefly. At the transmitter the control circuit is opened and closed in characteristically timed succession to radiate from the antenna the set of impulses corresponding to the character to be transmitted. This is accomplished b depressing a key upon the Teletype key oard causing the o ration of the cam shaft mechanism which under control of the key actuated selectors operates the transmitter contacts during the starting and selecting intervals of each signal to thereby effect radiation from the antenna system during each starting interval and thereafter either effect or prevent radiation from the antenna system during the five remaining selecting intervals. At the receiver this energy is reduced to a relatively low frequency and amlified, and operates the selective power reay which delivers the impulses to the me- The electron tube circuits operate to actuate the Teletype armature in the same order of sequence as the radiations are transmitted from the distant transmitter. The armature causes the proper positioning of the type wheel and operation of the print dog to print the proper character by the printer mechanism above described giving the result of a printed character simultaneously with the depression of that same lettered key at the distant transmitter keyboard.

Speeds are obtainable at the rinter receiver beyond that practicable y manual operation and messages may be transmitted in clear and concise order without the attendance of a radio o rator skilled in the code. It is particular y noted that the design of receiving system, electron tube circuit and power amplifier circuits, is such that the relay 90 and'printer control magnet 99 respond to the groups of impulses with little or no la The system to 5l practical purposes is substantlally secret inasmuch as the signals are not readable by aural reception. The system is capable of substantially secret operation by lntcrchange of t pe wheels at the receiver with a correspon ing change of designatinv caps upon the keys at the transmitter keyboard.

While the system has been described in connection with the Teletype printer it will be understood that other types of automatic' printers of a similar character may be employed and that impulses may be'automatically transmitted instead of by manual means and that no limitations upon the invention are intended other 'than are imposed bythe scope of the appended claims.

lll)

Having thus described my invention what I claim and desire to secure by Letters Patent of the United States is as follows:

1. A radio receiving system comprising in combination a plurality of electron tube circuits each arranged to respond to a characteristically timed succession of impulses of energy, a pair of electron tubes connected therewith each tube having grid, filament and plate electrodes connected in parallel, an input circuit for said tubes tuned to res ond to said impulses of energy, an output circuit for said tubes for delivering said impulses, means connected witli said output circuit for responding with negligible time lag to said impulses and mechanical means controlled by said means for selectively choosing a character represented by a particular succession of impulses in said electron tube circuits and for effecting the printing of such character.

2. A radio receiving system comprisingfin combination a plurality of electron tube circuits each arranged to respond to at least thirtyone separate sets of im ulses of energy extending through a de ite number of successive time intervals for each` character signal, a pair of electron tubes having grid, filament and plate electrodes connected in parallel, an input circuit for said tubes tuned to respond to said timed impulses oi energy, an out ut circuit for said tubes for delivering sai timed impulses of energy, mean-s for responding with negligible time lag. to each succession of timed impulses of energy and mechanical means controlled by said means for selecting a character represented by each 'succession of timed impulses of energ in said electron tube circuits and for causmg the printing of such character.

3. A radio receiving system comprising in combination-a plurality of electron tube circuits each arranged to respond to at least thirty-one separate and distinct groups of impulses of energy extending through at least five successive time intervals, a pan* o1 electron tubes having grid, filament and plate electrodes connected in parallel, an input circuit for said tubes tuned to respond to each of said five impulses of energy, an output circuit for said tubes for delivering each of said live impulses, a relay circuit arranged to respond with ne ligible time lag to each of said impulses, a ocal circuit controlled by said relay circuit and an electromagnet controlled b said local circuit having an armature an means controlled thereby on receipt of a particularsuccession of impulses of energy for effecting the selection and printing of a character represented thereb y JOHN B. BRADY. 

